Some packet networks include a packet switch that receives a packet having one transport identifier, such as a Virtual Local Area Network (VLAN) identifier, on one port and transmits a modified version of the packet having a different transport identifier, such as a Multiprotocol Label Switching (MPLS) label, on another port. Such packet switches modify the packet to have the different transport identifier prior to forwarding the packet through a switching fabric to a destination port of the packet switch.
This approach to modifying the packet may be slow, resource intensive, or both because the packet switch must select the transport identifier to be added to the packet at the ingress port of the packet switch. Typically, this involves not only determining which port of the packet switch the packet will be forwarded to, but also referencing a large lookup table that includes all of the transport identifiers that could potentially be added to the packet to determine which of the potential transport identifiers is to be added to the packet. Managing the large lookup table may require significant system resources, especially during failover operations in which the entire table may need to be transferred to a different hardware module.
Modifying the packet to have the different transport identifier at the ingress port may also unnecessarily consume switching fabric bandwidth associated with the packet switch. If the new transport identifier is lengthy, the switch may consume a significant amount of the switching fabric bandwidth in relaying packets that have been modified to include the different identifier.
These speed, resource, and bandwidth issues associated with conventional packet switches are particularly evident when conventional packet switches relay multicast packets and/or broadcast packets addressed to a plurality of destination ports.